add feature selection on submit car

I want that when a person sumbits a vehicle they can choose from features already listed .. under additional features. If there is a feature not there they should be able to add it in the area of other. At some point it would be nice if they add it and it goes into the data base that other peopkecan choose from that feature as well instead of me having to add them. But if that cost to much just fix this part fir now. Type 6467567 if you have read this.